The present disclosure is related to a photonic package structure, more particularly, to a package structure for disposing a flip-chip driver directly on a substrate or via an interposer to have a galvanically coupled output directly connected to a directly modulated laser (DML) chip with minimized inductance in a photonics transceiver module.
As science and technology are progressing rapidly, processing speed and capacity of the computer increase correspondingly. The communication transmission or reception using the traditional cable is limited to bandwidth and transmission speed of the traditional cable, but the mass information transmission required in modern life causes the traditional communication transmission overload. To address such requirements, the optical fiber transmission system replaces the traditional communication transmission system gradually. The optical fiber transmission system does not have bandwidth limitation, and also has advantages of high speed transmission, long transmission distance, its material is impervious to electromagnetic waves. Therefore, the electronics industry performs research toward optical fiber transmission which will become the mainstream in the future. Said optical communication is a technology in that light waves function as signal carriers and transmitted between two nodes via the optical fiber. Field of optical communication can be divided into optical communication side and electric communication side according to transmission medium. A key component of the optical communication side is optical transceiver which is configured to receive optical signals coming from optical fibers and convert to electrical signals capable of being processed by an IC, or to use a modulated laser chip to generate optical signals based on electrical signals and transmit the optical signals via optical fibers.
A state-of-art optical transceiver module is integrated with silicon photonics technology and packaged in a compact photonics module. In the photonics module, a directly modulated laser (DML) chip is usually coupled with a driver chip to receive control signals for generating optical signals to be transmitted into the optical fibers. FIG. 1 shows a schematic diagram of a driver chip being coupled with a DML chip via wirebonds according to a conventional packaging scheme. The wirebond, however, has high inductance, which distorts the current signal flowing into the DML. For example, a mere 200 pH inductance caused by a wirebond can substantially distort PAM-4 signal eye diagrams for ≥25 Gbaud rate data transmission. Therefore, an improved packaging technique is desired for coupling the driver chip with the DML chip. This does also potentially lower the power dissipation since electric circuitry required for signal conditioning might be omitted.